When you have set up your Sage Intacct web services user to Integrate between Intacct and AssetAccountant™.
You have reset the password to your web services user login.
It is critical that you use the details in the password reset email to log in to the Intacct UI and you reset the temporary issued password to a permanent password set by yourself.
Sage Intacct will not accept a temporary password to log in from a web service user like AssetAccountant™. And will return the error 'Invalid User Credentials'. On every log in attempt with this temporary password.